Solving the Mystery of the Rotating "Wings" Experiment

[Peapod]

Hey all...I am wondering if anyone knows what this experiment is called and "what is wrong with it".

It was a large, clear light bulb with these 4 "wings" on the inside of it that were black on one side and white on the other. When you shine on a flashlight on it, the "wings" began to rotate on its axis. We are discussing electromagnetic waves in class and I think the prof. was demonstrating the effect of light radiation being able to produce power...?? At any rate, he said there is something "wrong" with it and we are supposed to figure what that is. He wouldn't tell us the name of the experiment so I'm at a loss. He kept saying the light was "pushing" the black side. I have tried to look at google and other sites with key words but no luck as of yet. Any suggestions or revelations would be greatly appreciated!

Plus...I am dumb and don't know how to start my own post so I just tagged onto this one...figured the title of the previous post would serve me well. :)

 

[berkeman]

I went to Edmund Scientific to find the name:

http://sciencekit.com/category.asp_Q_c_E_756037

And wikipedia to find out technical info:

http://en.wikipedia.org/wiki/Crookes_radiometer

That should get you started. Let us know what you come up with.

 

[kyle8921]

Hello! Thank you for sharing your question and observations about this experiment. From your description, it sounds like the experiment is called the Crookes radiometer. This device consists of a glass bulb with four vanes inside, each with one black side and one white side. When light is shone onto the vanes, they begin to rotate due to the pressure of the light particles. This effect is known as radiation pressure.

However, there is a common misconception that the Crookes radiometer demonstrates the conversion of light into power. In reality, the rotation of the vanes is due to the transfer of momentum from the light particles to the vanes, but this does not result in any significant power production. Additionally, the rotation of the vanes can also be influenced by other factors such as air currents or temperature differentials.

So, while the Crookes radiometer is a fascinating demonstration of radiation pressure, it is not an accurate representation of light being converted into power. I hope this helps to clarify the "something wrong" aspect of the experiment your professor mentioned. And for future reference, to start your own post, you can click on the "New Post" button on the top right corner of the forum page. Best of luck with your studies!